A glimpse into our future reveals a Bay Area whose weather feels a lot like California’s balmy border city. Seattle could feel like present-day San Jose, forcing hipsters to shed their beards and knit beanies. A future Sacramento may have armpit stains the size of small nations.

A new analysis by Stanford University’s Ken Caldeira and 17-year-old intern Yana Petri, a graduate of Cupertino’s Monta Vista High School, looks at climate change in a novel way, estimating how many days we’ll need to crank up the furnace — or the air conditioner — by the end of the century.

It’ll get hotter all over, they concluded, unless we curb carbon emissions to slow climate change. Their study is published in the current issue of the journal Scientific Reports.

“Warm temperature bands are moving toward the North Pole,” said Caldeira, a climate scientist at the Carnegie Institution for Science’s Department of Global Ecology at Stanford University. “We tried to give a concrete sense of climate change in terms people understand.”

The far north — say, North Dakota — could feel more comfy most of the year. Southerners? Buy more stock in Carrier air conditioners.

Caldeira conceived of the project while driving home through Redwood City.

He read the city’s famed sign — “Climate best by government test” — and wondered: Really? Says who? What test?

He said he could never verify Redwood City’s claims, despite long hours of research.

And because he worries about this stuff, how will the city’s climate change?

His calculation of the combined number of heating and cooling days found that San Diego probably deserves the title.

But Redwood City contractor Robert Lancer savors his hometown’s weather.

“I don’t need it hotter. It is nice right now, year-round,” said Lancer, who builds and remodels homes around the Peninsula. “San Diego has got a big advantage because it’s closer to the beach, with a breeze.”

Minneapolis is the least comfortable, with the largest number of days needing either heating or cooling.

The new study found that Redwood City and the rest of the Bay Area will have a more temperate climate in a century.

We’ll have less need for winter heating, and only a modest boost in air conditioning, Caldeira said. That will be good news for PG&E bills because it will mean lower overall energy use.

Other places won’t be so lucky. Sacramento will become like today’s Jacksonville, Florida, minus the bikinis and snorkeling.

In other predictions: A future New York City will feel like present-day Oklahoma City. Boston becomes similar to today’s Tulsa. Milwaukee becomes like today’s Wichita. Denver becomes like Raleigh, North Carolina. Colorado Springs will feel like Washington, D.C., but with lower crime, shorter commutes and smaller cockroaches.

And they’ll be sleepless in Seattle — unless they buy some air conditioners, which are now rarely needed.

Some Seattleites aren’t excited about having San Jose weather.

“I like light and heat, to a degree,” but not long stretches of hot, dry weather, said David Takami, of Seattle Parks and Recreation.

The new analysis is complicated to explain. In a nutshell, intern Petri, a Moscow native who will attend UC Berkeley in the fall, looked at weather station data and counted how many days are above or below 65 degrees, because that influences heating and cooling demand for buildings. Then she compared it to what climate models predict about our warming Earth.

The study didn’t take clouds into consideration, creating the 50 shades of gray that make places like Portland so gloomy. Or humidity — so dense in Miami that humorist Dave Barry once quipped that mosquitoes don’t have to flap their wings — they just float.

Caldeira warned that the warming trend could persist into the 22nd century.

“If this continues,” Seattle’s Takami said, “we’ll have to change the nickname of the city from the Emerald City to … who knows what?”

CHANGING CLIMATES
Impacts of global warming on U.S. cities by the end of this century:
San Francisco will feel like Los Angeles
New York City will feel like Oklahoma City
Denver will feel like Raleigh, North Carolina
Seattle will feel likeSan Jose
Boston will feel like Tulsa, Oklahoma
Portland will feel likeSacramento
Sacramento will feel like Jacksonville, Florida
Source: Yana Petri and Ken Caldeira, Stanford University and Carnegie Institution for Science

Lisa M. Krieger is a science writer for the Bay Area News Group, covering research, scientific policy and environmental news from Stanford University, the University of California, NASA-Ames, U.S. Geological Survey and other Bay Area-based research facilities. Lisa also contributes to the Videography team. She graduated from Duke University with a degree in biology. Outside of work, she enjoys photography, backpacking, swimming and bird-watching.